In some heat pump installations, it is known to arrange a supplementary electric heater in order to provide an additional boost of the performance of the installation under specific conditions. Such a supplementary heater may for instance permit the heat pump of the installation to operate at lower ambient temperatures. Moreover, the supplementary heater may permit an increase of the temperature to such a level that bacteria and other microorganisms may be removed from hot tap water.
Such existing supplementary heaters are suffering from different disadvantages of being space consuming, requiring complex connections and installation, lacking modularity and flexibility, and requiring many welds increasing the risk for leakage.
WO 2012/101273 discloses a heater to be connected to a plate heat exchanger having inlet and outlet ports. The heater comprises two plate pairs with two inlets for a medium to be heated and two outlets for the medium. Each plate pair comprises a first plate comprising a first main surface and a second plate comprising a second main surface. The first plate and the second plate are attached to each other and enclose a respective flow channel for the medium between the first and second plates. The plate pairs are arranged beside each other with a space between the plate pairs. An electric heating element is provided in the space between the plate pairs. Each plate pair defines a flow channel. The flow channels are not directly connected to each other but via external pipes.
U.S. Pat. No. 6,421,501 discloses another heater to be connected to a plate heat exchanger having an inlet port and an outlet port. The heater comprises a plurality of chambers, each comprising a first plate and a second plate spaced apart by a spacer, which together form a flow channel for a medium. The first and second plates form a respective electrode for heating the medium.